It is conventional in industries involving the transportation or storage of abrasive materials, such as coal, various mineral ores, or other abrasives, to provide a steel backing or liner for the wall or surface to be protected, and thereafter to weld specially prepared abrasion resistant ceramic tile or bricks to the backing.
Such bricks are commonly one inch thick fired silicon ceramic, such as an aluminum-silicon oxide or a silicon carbide compacted under high pressure from a dry powder and optionally with a suitable binder. The typical brick has four by six inch faces, although the dimensions may vary appreciably, say from one-half to two inches in thickness, with faces ranging from less than four inches in the shorter dimension to more than nine inches in the longer dimension. Also the brick may be molded from a molten abrasive resistant material such as basalt or an aluminum-zirconium-silicate.
A common weldable brick is formed with a central welding hole about one inch in diameter that extends through an outer face of the brick and is constricted slightly adjacent to the opposite inner face to confine a weldable metallic insert. The latter is inserted into the larger or unrestricted opening of the welding hole and is retained adjacent to the restricted end by friction. With the welding insert arranged coaxially in the hole, the metal insert is welded to the steel backing or liner, either by conventional MIG (metal inert gas) welding or in rare instances by conventional use of an arc welding rod. Thereafter a cylindrical closure plug is inserted into the unrestricted opening of the welding hole to close the same.
In some instances, it is preferable to weld the metal insert by conventional arc welding to the steel backing or liner, but arc welding is not particularly convenient with the type of brick described because it is difficult to maintain the metal welding insert in a coaxial position at the reduced end of the hole. The welding insert is provided with a central opening through which a welding rod or wire must pass in order to contact the steel wall or backing. When the welding rod is extended through the aforesaid central opening in the welding insert, the latter is frequently knocked out of alignment by the rod and welded in a cocked position to the steel liner. A similar problem arises even during MIG welding when the MIG welding wire is inserted through the welding insert into contact with the steel backing or liner to which the brick is to be secured.
Not only will the resulting weld be less secure, but the cocked insert in some instances prevents the cylindrical closure plug from fitting flush with the outer surface of the brick. The plug will thus be subjected to excessive abrasion and will rapidly wear away. Furthermore, although the cylindrical plug is usually cemented within the welding hole, it frequently works loose even when it is flush with the outer surface of the brick, whereupon the metallic insert will rapidly wear away by the abrasive action and the entire brick will be dislodged.
Even if the metallic insert is properly located and welded to the steel backing, the cylindrical closure plug cannot extend axially within the welding hole to the extent desired because a certain amount of space must be allowed to accommodate the situation when the metallic insert is cocked out of its coaxial alignment within the hole. Accordingly, the wear resistant thickness of the brick at the region of the approximately one-inch diameter welding hole will be considerably less than the thickness of the adjacent portions of the brick. When the thinner cylindrical plug eventually abrades away, the metallic welding insert is rapidly disintegrated by abrasion at the exposed hole.
In addition, the one inch centrally located hole tends to weaken the brick across the diameter of the hole. In consequence, the comparatively brittle ceramic brick tends to break when subjected to impact during use, or when the installer of the brick attempts to break off a portion in order to provide a close fit near the edge of the wall to be lined. In that event, the brick tends to crack at the middle through the one inch hole instead of at the region where the craftsman's hammer strikes the brick.
An additional objection to bricks of the type described is that three loose pieces are required, i.e., the brick, the insert, and the cylidrical plug. The insert may be cemented in place, but the cementing involves an additional operation and increases the cost of the brick.
Important objects of the present invention are to provide an improved brick of the general type described and a method of using it that avoid the above noted objections; and in particular to provide an improved weldable ceramic brick having an insert receiving recess opening at its inner face, i.e. the face that confronts the wall or substrate to be protected, to receive a deformable weldable insert, which after being inserted into the recess through its opening at the inner face of the brick, is deformed into undercut portions of the recess by force applied against portions of the insert exposed at the latter opening, thereby to frictionally and mechanically interlock the insert and brick.
Another important object is to provide a weldable brick where, instead of a one-inch hole extending approximately through the entire brick, only a small diameter guide hole large enough for insertion of a welding wire as customarily used in MIG welding, or a slightly larger diameter guide hole for a conventional arc welding rod, extends centrally through the brick from its outer face toward its inner face.
The guide hole may be as small as approximately 0.035 inches in diameter and no larger than one-eighth of an inch in diameter where MIG welding is available, or may be approximately three-sixteenths of an inch in diameter if it is required for guiding a conventional arc welding rod, and may extend about three-quarters of an inch into a one-inch thick brick from its outer face, whereupon the guide hole enlarges radially to a maximum of approximately a square inch in cross sectional area to provide a recess having an insert receiving opening at the aforesaid inner face of the brick and having a plane ceiling normal to the axis of the guide hole and parallel to the inner and outer faces of the brick. The periphery of the recess adjacent to its ceiling is undercut into the sidewalls of the recess to provide a larger cross sectional area than the insert receiving opening at the inner face of the brick. Thus the maximum radial or transverse dimension of the recess comprises an enlargement or an undercut with respect to the aforesaid insert receiving opening for receiving edge portions of a sheet steel welding insert.
A one-piece metallic welding insert is provided with a plane base having a central hole coaxial with and sufficiently larger than the guide hole through the brick to enable free passage of a welding wire or rod. The base also has diverging prongs or outer edge portions that define an area approximately the same as the area of the insert receiving opening, but slightly less to enable insertion of the insert freely into the recess through that opening. The prongs or outer edge portions are dimensioned so that when the insert is inserted, prongs first, through the insert receiving opening, and the base of the insert is pressed toward the ceiling of the recess, the prongs will slidably engage the ceiling and be deformed radially or transversely of the guide hole into the undercut portion of the recess. Thus the insert will be interlocked rigidly within the brick. At the interlocked position, the plane of the base of the insert will be spaced sufficiently from the inner surface of the brick and within the recess to enable formation of a pool of molten welding rod between the base and the steel backing for the chute or other wall to be protected.
In a modified form, a metallic insert has its deformable outer edge portions generally square in section transverse to the guide hole. The insert receiving recess is also square in cross section to closely receive the insert and is undercut adjacent to its ceiling to receive the corners of the square edge portions when the insert is located within the recess and rotated 45.degree.. In this situation the corners of the square edge portions prior to the rotation decline slightly away from the ceiling. Thus when the insert is rotated, the edge portions are deformed or bent upwardly toward the ceiling by cam action as they enter the undercuts. The resulting deformation of the insert frictionally interlocks it within the recess. The central hole in the base of the insert and coaxial with the guide hole is preferably out-of-round for receiving a mating tool to enable rotation and interlocking of the insert within the recess.
After the metallic welding insert is deformed and interlocked within the recess, the brick may be shipped as a weldable unit to the site where welding is desired. The brick is then held with its inner face adjacent to the steel wall or backing to be protected and welded in place by conventional MIG or arc welding. A conventional welding rod or MIG welding wire is inserted through the small guide hole in the brick and thereby guided through the coaxial hole in the base of the welding insert and into welding contact with the steel backing without touching the insert.
The weldable brick described is particularly suitable for conventional arc welding because the small diameter guide hole guides the arc welding rod coaxially through the larger hole in the base of the welding insert and into welding contact with the steel liner without disrupting the coaxial alignment of the insert. The heat of the arc melts the tip of the welding rod which flows into contact with both the base of the insert and the steel backing to complete the weld. However where MIG welding equipment is available, the brick described can also be readily welded similarly to the steel backing by conventional MIG welding.
By virtue of the improved construction comprising the deformed welding insert frictionally and mechanically interlocked within the undercut recess, the insert cannot be inadvertently pushed out of its alignment within the recess and a weld of optimum strength and effectiveness is thus readily accomplished. Welding the brick at any angle of support to the steel backing and especially overhead is facilitated with consequent reduced welding time and labor cost. After the weld, the small diameter guide hole through the brick may be sealed with a caulking material, but such caulking is not essential because the hole is too small to cause serious damage to the brick by abrasive material moving across its outer surface. Also by virtue of the undercut recess for the welding insert, occupying approximately only one-forth of the thickness of the brick, the major thickness of the brick is available for resisting abrasion and the abrasion resistant life of the ceramic brick is materially increased. Likewise a plane of weakness through the diameter of the recess for the welding insert is minimized because that recess only extends approximately one-forth of the thickness of an inch thick brick, whereby the latter can be hammer cut to a desired size by a craftsmen without breaking the brick through the recess.
In a typical construction, the small diameter guide hole for the welding rod and the recess for the welding insert is formed while the brick is soft, i.e. during its initial formation by conventional molding processes, especially when the recess for the welding insert is formed with a rectangular cross section. Conventional cam operated die parts can then be used to form the undercut recess and thereafter retracted from the molded brick. The brick can also be molded with only the guide hole for the welding rod or wire extending therethrough. Thereafter, while the brick is still soft and before being fired, an undercut insert receiving recess may be cut in the inner face of the brick coaxially with the guide hole. In either case, after the brick is formed to the desired shape for receiving the welding insert, it is fired and hardened by conventional processes.
Another object of this invention is to provide an improved weldable brick comprising the inserted, deformed, and interlocked welding insert substantially as described, and a method of using the same wherein the guide hole may be eliminated in situations where welding access to the exterior of the sheet steel wall or substrate to be protected is convenient. In such a situation, a hole is burned or otherwise formed through the sheet steel wall from its outside, i.e. its surface opposite the surface to be protected. The latter hole is dimensioned to enable insertion of a welding rod or MIG welding wire and is located coaxially with the center of the welding insert in the brick. Thereafter the welding rod or wire is inserted through the hole in the steel wall and into contact with the edges of the latter hole to form a molten pool joining the steel wall and metallic insert interlocked within the brick as described above. Also in the situation described, the base of the metallic insert need not be provided with a central hole for passage of a welding wire or rod.
Another object of this invention is to provide weldable bricks of the type described but dimensioned for lining a pipe used for conveying an abrasive slurry or pneumatically transporting abrasive particulates. It has been conventional to line such pipes with abrasion resistant ceramic bricks extending longitudinally of the pipe and having truncated triangular cross sections arranged to fit closely together adjacent to the pipe's inner periphery. Commonly the bricks would be cemented in place, as for example by forcing cement longitudinally of the pipe within the chordal space between the pipe and each adjacent brick. The cementing often causes small amounts of cement to enter spaces between the bricks, so that the space for the last brick can seldom be predetermined.
When all but one of the bricks are installed around the interior circumference of the pipe, the remaining space is filled by a key brick that locks all of the others in place. In order to assure a tight fit for the key brick, it is frequently diamond cut to size and then hammered into place, an expensive and time consuming procedure. Furthermore, during use of the pipe, the abrasive slurry rapidly wears away the cement between the bricks, such that the key brick sometimes loosens and falls out, whereupon the remaining bricks associated with the loosened key brick also fall out of place.
In many instances where the pipe is used for conducting an abrasive slurry, only a lower portion of the pipe is in contact with the slurry. Consequently the expensive ceramic lining for the upper portions of the pipe, required only because of the key brick, are not used unless the pipe line is disassembled and the individual pipes are rotated at least approximately 120.degree., then reassembled.
In accordance with the present invention, ceramic bricks shaped overall in accordance with conventional practice, but provided with welding inserts as described, are welded to the inner periphery of the pipe. Thus a key brick is rendered unnecessary and, where feasible, only approximately the lower half of the pipe is lined with the ceramic bricks, with obvious savings in material and labor. Where the type of use requires the entire interior circumference of the pipe to be lined, this is readily accomplished, but a tight and precise fit for the final or "key" brick is unnecessary and the expense of diamond cutting is avoided. Likewise no cement that can readily be abraded away is required to secure the bricks in place, but where cement is used, its abrasion causes no concern because the bricks are secured in place by welding.
In many instances, the abrasive material is highly corrosive, such that metallic pipes or steel walls cannot be employed, even when lined with abrasive resistant bricks as described herein. In such instances the walls and pipes are manufactured from dielectric corrosion resistant materials to which the weldable bricks cannot be welded. It is accordingly another object of this invention to modify such walls or pipes to enable their use with the weldable bricks of the present invention.
Specifically, weldable grommets or buttons made from corrosion resistant material, such as stainless steel for example, are secured within the side walls of the wall or pipe at locations coaxial with the welding inserts of the bricks. Thereafter the welding inserts are welded as described above to the grommets or buttons by otherwise conventional welding technique.
The art involving the molding and firing of ceramic material from which bricks embodying the present invention are made is highly developed and capable of manufacturing weldable bricks as described having undercut insert receiving recesses of various shapes and sizes in accordance with this invention. The brick may be compacted from a dry powder within a multiple part mold under approximately 3500 psi (pounds per square inch) to produce a green unfired brick containing recess forming inserts that when removed leave the desired recess. However the forming mold for the green unfired brick can be complex and may require a number of recess forming mold inserts.
Another important object of this invention is to provide an improved weldable brick of the type described wherein the recess forming inserts can be readily removed from the comparatively soft and friable green brick without damaging it immediately after it is compacted. The resulting insert receiving recess is undercut at its opposite ends, but the undercut at each end is offset laterally from the offset at the opposite end.
At each end of the recess laterally of the undercut at the same end, the recess is defined by an end wall that slopes endwise toward the ceiling from its respective end of the recess opening for approximately 20% or less of the length of the recess, then merges with the recess ceiling. The recess is formed by placing a pair of identical independently removable recess forming inserts side-by-side in the mold. Each removable insert forms a lateral half of the recess, i.e. one lateral portion of the ceiling spacing one sloping wall and the one undercut at the opposite ends of that lateral half. After the powdered material of the brick is compacted under high pressure, each separate recess forming insert is withdrawn from the undercut formed thereby and moved outwardly of the recess as enabled by the associated sloping wall. Thereafter the green brick is fired and hardened.
The weldable insert is preferably formed from a sheet steel blank to provide legs at its opposite ends dimensioned to fit within the opposite undercuts of the recess when deformed therein. In its undeformed conditions, it may be generally V-shaped and is readily insertable through the recess opening, with its legs diverging outwardly at approximately 110.degree. from a central apex of the V toward the recess ceiling. Once inserted, pressure flattens the apex toward the ceiling and thereby forces the opposite ends of the legs into interlocking engagement within the undercuts. The weldable insert may or may not be provided with a central opening for passage of a welding wire or rod, depending on whether or not the brick is to be welded to a supporting wall from the outer face of the brick opposite the recess opening.
The concept of the weldable brick having an undercut recess opening at its inner face an a weldable insert deformed and interlocked within the recess also enables other useful abrasion and shock resistant structures that do not require welding. It is accordingly another important object of the invention to provide recessed bricks as described herein interlocked with either a thermosetting or thermoplastic sheeting or surface without recourse to welding. In one embodiment by way of example, a number of ceramic bricks as described herein are placed outer-face down on the surface of a temporary supporting mold or frame having a peripheral raised border. Thereafter a hardenable liquid plastic, reinforced as for example by glass fibers if desired, is poured over the upwardly opening recesses in the inner faces of the bricks to any desired thickness, say one-quarter inch to an inch or more. The plastic readily fills the recesses and interlocks with the metal welding inserts and, when hardened and removed from the supporting frame, provides an abrasion and bullet resistant panel or structure. The term "plastic" as used herein includes any suitable thermoplastic or thermosetting plastic, including various suitable resins, such as epoxy resins.
The various ceramic bricks may be rectangular or hexagonal in shape for interfitting closely with each other, or may be of any desired shape if such interfitting is not important. The surface of the supporting mold or frame may be shaped so that the resulting abrasive resistant panel or structure will conform to any desired surface to be protected, such as a chute for abrasive materials, or surface portions of a military vehicle. When the abrasion resistant panel is other than flat, the surface area of the ceramic bricks may be comparatively small so that adjacent bricks may conform to various curvatures. Likewise when necessary the panel may obviously be formed between opposing mold parts according to conventional molding practice.
Finally, abrasion or shock resistant panels or structures may be formed as described above without recourse to the above described weldable inserts, merely by emphasizing the undercuts of the recesses in the ceramic bricks. The fluid hardenable plastics will fill the recesses and interlock within the undercuts when hardened.
Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.